Actuators are used to remotely operate the valves for controlling the flow of fluids.
Several designs of the actuators are known which convert reciprocating linear motion into bi-directional rotation; GB 2225079A being one such patent. In such design, linear motion in one direction is caused by injecting pressurized fluid (generally air) which acts on pistons, held at that location by mechanical energy accumulators, like compression springs. While pistons move, they also compress the springs, thereby accumulating energy in them. As the pressure is released, the pistons are made to move back consequent to springs releasing the accumulated energy.
The energy accumulators are generally tough springs needing several kg of force to compress and assemble them in the actuator.
There is need to change the operating torque of the actuator so as to synchronize it with the air pressure available, torque of the valve and the type of the valve. The seals and gear arrangement inside the actuator need regular maintenance; and therefore, energy accumulators need to be removed at regular intervals and re-assembled, thereby needing skill and fixtures to assemble, which is time consuming and resulting in increased downtime.
In another prior art, disclosed in WO2010/063514 A1, instead of one or more concentric big compression springs, several small compression springs are used, axially parallel to one another to solve the problem of variable torque needed as discussed above. However, this arrangement is not efficient since the ratio of “length to diameter” of the parallel springs is more than the limit, above which spring is not able to maintain its axis straight under energy accumulated i.e. compressed condition. Due to such “buckling”, the coils of spring entangle and disentangle during operation, producing noise and adversely effecting the response time of actuators.
Our invention solves both these problems.